Synthesis of spiroindolo[2,1-b]quinazolines from Huisgen zwitterions and tryptanthrin-malononitrile adducts

Functionalized spiroindolo[2,1-b]quinazolines are obtained from the reaction between tryptanthrin-malononitrile adducts and Huisgen zwitterionic intermediates, generated by addition reaction of aromatic N-heterocycles with acetylenic esters. The reaction is diastereoselective leading to the formation of a single diastereoisomer. The structure of a typical product established by X-ray crystallography.